Conventional laboratory testing and measurement systems are comprised of at least two components: an instrument and a cartridge. The instrument provides power and excitation signals to perform a given assay and measures generated signals to ultimately quantify the result of the said assay. The cartridge can be inserted into the instrument and provides an interface between the instrument and the assay.
The cartridge is replaced and/or is disposed of at the end of each assay. A new cartridge may be inserted into the instrument at the beginning of the next assay. In most applications, the disposable cartridge is inserted into the instrument through an opening at the beginning of the new assay. This opening can be a door, a slot, or a compartment built into the instrument to receive the cartridge. In some assays, reagents flow within channels or inside the cartridge. The reagents transport biological and/or chemical moieties relevant to the assay from input reservoirs into different compartments within that cartridge. The fluid motion leads to pressure variations between different segments or channels of the cartridge. The fluid motion also leads to pressure differences between the inside of the cartridge and the ambient pressure. As such, cartridge walls are normally built so that they are thick enough to withstand and tolerate pressure differences between its channels and the ambient pressure.
However, in certain applications, the instrument generates an excitation energy (e.g., electromagnetic, acoustic, thermal, etc.) that needs to couple strongly to the cartridge channels and/or compartments. The coupling may require close proximity between the excitation source and the internals of the cartridge. In such cases, the cartridge wall that separates the cartridge channels from the excitation source of the instrument must be as thin as possible. The thin wall geometry is prone to inflation of cartridge flow channels and other features due to hydraulic flow pressure. This necessitates a proper clamping mechanism over the cartridge to prevent uncontrolled changes to fluidic dimensions during an assay run.
The conventional solution to this problem has been to include a mechanical instrument door (interchangeably, lid) that closes over the cartridge. The mechanical lid provides support needed to prevent the cartridge channels from inflating or changing shape. This approach works relatively well when the disposable cartridge is relatively narrow (e.g., only a few centimeters wide), featuring a single set of channels at its center. When the cartridge features a multitude of parallel assays with multiple sets of channels spread over a relatively large width (e.g., over 4-5 cm wide), it becomes significantly more difficult to establish and maintain uniform back-pressure over the cartridge using the mechanical lid approach.
FIG. 1A schematically illustrates the vertical pressure on a conventional cartridge maintained under a mechanical lid. In FIG. 1A, stress simulation of a simple mechanical lid structure that uses quarter-inch thick plates of aluminum and silicone rubber, respectively, to press on a cartridge several millimeters thick. For simplicity, the bottom support is assumed to be thick steel which is constrained from moving. A narrow distribution of mechanical force (spread across approximately a one eighth inch (⅛ in.) distance) at the center top of the aluminum plate presses down on the sandwich structure. The simulated case roughly corresponds to a lid latch or an over-center clamp holding the applied force over the aluminum plate.
FIG. 1B graphically represents the pressure under the cartridge across its width. It should be noted that the pressure over the cartridge surface is highly non-uniform—peaking directly under the location of the applied force, and going negative near the edges. The negative pressure indicates that the aluminum-silicone lid is bending downward at the center and upward near the cartridge edges. This is highly undesirable.
The root cause of this shortcoming is the fact that the lid ends up being used to transform a mechanical force (often originating from a point or a small region, such as the hinges or latch of a door) into a uniform pressure over a wide cartridge surface. The wider the cartridge, the thicker, stiffer and heavier the mechanical door will need to be to supply acceptably uniform pressure over the entirety of the cartridge.
Accordingly, there is a need for a system, method, and apparatus to provide substantially uniform support over a cartridge lid configured to work with a measurement instrument.